There are numerous diseases associated with movement of material through the gastrointestinal tract, in particular the esophagus. To observe the movement of material, such as food or liquid, through the esophagus, the pressure exerted by the esophagus may be measured as the material moves through the center of the esophagus. This results in pressure values as a function of time and location of in the esophagus. In some cases, impedance measurements are also made along the esophagus. The measurements of the esophagus may allow physicians and caregivers to compare healthy, normal movement in the esophagus to abnormal or possibly diseased movement, as well as to monitor changes in an abnormal or diseased esophagus in response to medical treatment.